The present invention relates in general to radially adjustable cutting tools, and in particular to a new and useful apparatus for the fine adjustment of the cutting edge of a tool mounted in a rotating radial adjusting head.
Known boring heads are used preferably for the treatment or cutting of hollow cylinder surfaces with a cutting edge of a tool that is radially adjustable with reference to the axis of rotation of the boring head. The tool is adjusted by means of hydraulic pressure. The boring head generally includes a radial adjusting head which provides a stiff parallel spring joint for guiding the turning tool, which comprises the cutting edge of the tool. The stiff parallel spring joint can be defected radially by small amounts by means of a piston or by means of an expansion element. A pneumatic control pressure (generally an air pressure) is transformed into a higher hydraulic working pressure which is applied, as an adjusting pressure to the adjusting member, over a pressure intensifier which is assigned to the boring head. During this operation, pressure oil can be supplied from a storage reservoir if, in the hydraulic arrangement, steering losses occur (see the German patent No. 24 26 409).
In order to compensate losses of waste oil, the piston of the pressure intensifier is retracted at the start of each treatment procedure, so that a vacuum is formed in the area of the pressure oil, which opens a back-pressure-valve, so that the pressure oil in the storage reservoir which possibly is under a slight over-pressure, can flow into the liquid chamber of the pressure intensifier.
Since a rotating system has to be balanced, in the known arrangement the storage reservoir and the back-pressure valve are disposed opposed to each other in relation to the axis of rotation. Nevertheless balance errors occur by reason of the stock of waste oil flowing slowly into the hydraulic pressure system, and balance errors cause oscillations. In addition to this the stock of oil has to be small in order to avoid overly high forces due to inertia, which would disturb the rotation. In order to keep these undesirable effects as small as possible, the arrangement has to be stopped frequently, in order to replenish the supply oil. Furthermore the control air has to be supplied through a rotary seal which has to be lubricated continuously, because otherwise the seal lips can be quickly destroyed at high rates of rotation. If the pressure intensifier and the radial adjusting head should be fashioned as construction elements which are spaced from each other, the pressure oil has to be supplied to the radial adjusting head through a rotary transmission with a rotary sealing as well. This is not very easy to carry out by reason of the high adjusting pressures and the strains of the rotary transmission related to these pressures. The rotary transmission thus is subject to premature wear.